Shaken and stirred

Published
12:00 am CDT, Thursday, October 16, 2014

More than 570,000 Illinois residents shook and rattled Thursday as part of an international earthquake drill to highlight the potential for quakes in some parts of the state previously thought fairly safe.

The U.S. Geological Survey this year updated maps showing the potential for seismic activity in the United States, upgrading the possibility of threats — and putting Illinois among the 16 states at highest risk of earthquakes.

Morgan County, along with Cass, Menard, Brown and Schuyler counties, is among a section of the state that could face “strong” effects from earthquake activity. Macoupin, Greene and Scott counties are among those that could see “very strong” effects from seismic activity, and Pike, Jersey and Calhoun counties could see “destructive” results, according to Illinois Emergency Management Agency maps.

Illinois is at risk from two major seismic zones, the Wabash Valley Seismic Zone and the New Madrid Seismic Zone. The Wabash Valley zone is between southeastern Illinois and southwestern Indiana. The New Madrid zone is in the central Mississippi Valley and includes portions of Alabama, Arkansas, Illinois, Indiana, Kentucky, Missouri, Mississippi and Tennessee. During any 50-year time span, there is a 25 to 40 percent chance of a magnitude 6.0 or greater earthquake in this zone, according to the Illinois Emergency Management Agency.

There have been more than 3,000 earthquakes recorded in the New Madrid zone since 1974, but most have been under a 5.0 magnitude and barely noticed, according to authorities.

Still, one of the most powerful earthquakes in the continental United States took place in this zone in 1811-1812, at a time the area was sparsely populated. A similar series of quakes today would cause an estimated $60 billion to $80 billion in damage, according to the Illinois Emergency Management Agency.

Western Illinois University geology professor Leslie Melim said the research from the recent activity increases the incentive to better define the hazards from earthquakes.

Melim said the new map defines the maximum expected ground motion based on a combination of earthquake history.

“This map better defines the areas that are at risk,” Melim said. “The greatest impact is really in engineering for new buildings. The greater hazards in southern Illinois should mean stronger building codes. It also means buildings in ‘safer’ areas can be built to lesser standards. For example, homes in earthquake areas must be bolted to the foundation and the foundation needs to be better attached to the earth underneath.”

WIU health sciences assistant professor Heriberto Urby has done extensive research and teaching on how people can prepare for an earthquake. He said one of the easiest and most important preparation steps is to assemble an emergency kit of supplies and provisions to be used in case of a natural disaster.

“Citizens and students should engage in training, drills, tabletop and other exercises, evacuation planning and other preparedness activities to become more adept and knowledgeable to be ready in the event an earthquake occurs,” Urby said. “Since Illinois is one of the states that could experience an earthquake, and perhaps even is at risk of increased shaking during an earthquake, according to the new seismic maps and studies, it is indispensable that everyone learns what to do to prepare for such a disaster.”